2016 saw a bleaching event that was the worst coral die-off we’ve ever recorded, and now a 2017 event makes matters worse. ARC Centre director Terry Hughes said the impact of back-to-back bleaching sprawls across 900 miles; only the southern third of the Great Barrier Reef is unharmed. It’s the second time in only 12 months scientists have recorded mass bleaching in the reef after aerial surveys.

And 2017’s bleaching can’t be explained away by El Niño. Hughes said the bleaching “is caused by record-breaking temperatures driven by global warming.”

The Great Barrier Reef has experienced severe bleaching in 1998, 2002, and now 2016 and 2017, according to scientists. Kerry said bleached corals don’t always die, but take at least a decade to make a full recovery, so with back-to-back bleaching they expect coral loss. Tropical Cyclone Debbie didn’t help either. The storm may have left damage in its wake when it hit part of the Great Barrier Reef at the end of March.

Hughes said in a statement, “Clearly the reef is struggling with multiple impacts. Without a doubt the most pressing of these is global warming. As temperatures continue to rise the corals will experience more and more of these events: one degree Celsius of warming so far has already caused four events in the past 19 years. Ultimately we need to cut carbon emissions, and the window to do so is rapidly closing.”